This invention relates generally to improvements in a dust abatement device and to a method of dust abatement, and more particularly to a device of this type that can be used in combination with a continuous mining machine to reduce the area of dust concentration created by the operation of such machine.
The basic function of a dust abatement device (air scrubber or wet dust collector) is, of course, to clean dust and/or contaminated air, and is accomplished in three basic steps. The first step is to convey the dirty air into the device by an air mover which is usually a fan that is any one of several different types, as for example, propeller, radial, squirrel cage and the like or any one of various types of positive displacement air movers. The only requirement is that the air mover be capable of moving the quantity of air desired and at the same time be capable of moving this air against whatever static air pressure is required by the type of device used. Heretofore, moving the air and abating the dust have generally been separate functions.
The second step is to mix the contaminants in the dirty air with a liquid by any one of various means including: (1) merely bubbling the dirty air through a pool of liquid, which is very inefficient. (2) mechanically atomizing the liquid through spray nozzles or other means and dispersing these liquid particles throughout the dirty air, usually in an enclosed compartment, thereby depending on numerous small particles of liquid to mix with or "wet" the particulate matter in the dirty air. This method, in order to obtain any worthwhile mixing efficiency requires a relatively large mixing chamber. (3) injecting the liquid and dirty air into a cylindrical chamber of a cyclone in such a way that the mixture spins around the chamber so that the heavy particulate matter and liquid tend to spin to the outside, mix together and run downwardly to the bottom of the cyclone where it is drained out of the bottom, the lighter air or gas being allowed to escape from the center of the chamber where the centrifugal force has been largely dissipated. Both wet and dry cyclone dust collectors have been used for various purposes, the wet type being referred to previously. Naturally, the higher the velocity of the dirty air entering the cyclone, as well as the smaller diameter of the cyclone tends to increase the collection efficiency of the cyclone. (4) mixing the liquid and the particulate contaminant that is in a gas by so-called "wet plate impingement". In this method, the high velocity of dirty air is directed against a wetted surface, and air is diverted from such surface. The inertia and mass of heavier solid particulate matter tends to make it strike or impinge on the wetted surface and hence be trapped by the liquid. Of course, the smaller and lighter the particulate, the harder such particulate has to be forced into contact with a wet plate and thus be mixed with the liquid. Wet plate impingement can be accomplished in two different ways. The first method is, as mentioned, with stationary plates and using high velocity air movement to provide the necessary inertia force for the particulate. The second method is to move the wet plates at high speed through relatively calm dirty air. Both methods serve the same purpose, that is to mix solid particulate matter (wetting action) with the scrubbing liquid.
The third step necessary in this type of dust abatement device is that the dirty mixture of solid particulate matter and liquid must now be removed from the main air stream, and thereby provide relatively clean air. Many devices heretofore utilized in mines in an attempt to clean up the foul air are of relatively large size and are of awkward shapes and configurations that preclude advantageous location of such devices near the mine face. Such devices are placed in the mine tunnel at a relatively remote location from the mine face behind the continuous mining machine. The heretofore conventional devices do not direct the clean air back toward the mine face, but rather, because of their structure and configuration, serve to direct the clean air rearwardly from the mine face. Moreover, such devices are not adapted to be carried by the continuous mining machine because such is prohibited by the bulk and shape of such devices. There is no provision on the device for permitting such functional and structural cooperation. As a result, such devices fail to cooperate with the mining machine in an effort to save the useful coal dust that is removed from the polluted air and to remove such dust with the mine material to a remote location.